Although a completely flat-surfaced wheel would be aerodynamic, it would also be hard to keep cool – especially during the braking process. An experimental new wheel rim, however, has cooling vents that open as needed … and they're activated by heat.
Called the Active Aero Wheel, the device is being developed by German tech startup CompActive. It's designed to minimize the airflow-disrupting vortices which form at high speeds around traditional ventilated automobile wheels, while still allowing the heat generated when braking to escape.
The vents take the form of five leaf-style flanges cut into the rim's flat metal surface, which remain flush with the rest of the surface most of the time. Adhered to the back/base of each flange is a lightweight actuator, which incorporates several shape-memory alloy wires arranged lengthwise, side-by-side.
As long as things stay cool inside the wheel, those wires stay in their default state. When they're heated, however, they contract. As they do so, they pull back on the flange, causing it to open inward. It's a clever setup, in that the heat generated during the braking process first causes the vents to open, and those vents then allow the heat to escape. Once the wheel has cooled back down, the vents close up again.
CompActive is currently inviting inquiries from parties interested in commercializing the technology. The Active Aero Wheel is demonstrated in the video below.
Source: CompActive